The PCF85263A is a CMOS Real-Time Clock and Calendar (RTCC) which offers low power consumption, drawing just 0.28μA at a supply voltage of 3.0V and an ambient temperature of 25°C.

It also provides for continued operation in the event of a power-supply outage. A battery back-up circuit automatically switches to battery power on the loss of the main power supply.

The PCF85263A counts years, months, days, weekdays, hours, minutes, seconds and 1/100th seconds, using a 32.768kHz quartz crystal. The clock may also be configured as a stopwatch or elapsed time counter.

Three time-stamp registers are available, triggered by the battery switch-over function as well as by input-driven events. The RTCC also features two independent interrupt generators, and provides pre-defined interrupts at every second, minute or hour. Frequency adjustment is made via a programmable offset register.

The PCF85363A offers the same functions as the PCF85263A, but with the addition of a 64byte battery-backed RAM.